Thermostatic coil



June 30, 1925.

l.. A. M. PHELAN THERMOSTATIC COIL Filed Sept. 22. 1924lll/11111111111111111111- l Patented ,lu-ne 30, 1,925.`

g UNITED STATES 1,544,342 PATENT OFFICE.

' LOUIS A. M. rnnmm, or BELOIT, WISCONSIN, ASSIGNORro-ABSOLUTEcoN-'IAc-TOR CORPORATION, or BELOIT, WISCONSIN, A CORPORATIONOF ILLINOIS.

THERMOSTATIC COIL.

Application leo. September 22, 1924. Serial No. 739,005.

To all whom t may (2o/noem.'

Be it known that I, LOUIS A. M. PIIELAN,

a citizen lof the United States, residing at Beloit, in the county ofRock and State of Wisconsin, have invented new and useful Improvementsin Thermostatic Coils, of which the following is a full, clear, concise,and exact description, reference being had to the accompanying drawing,`forming a part of this specification.

My invention relates to thermostatic coils and more particularly to la'device of this type wherein the bi-metallic strip is provided with animproved means for'efl'ecting an increased efficiency in the expansionand contraction thereof.` l

It is commonly known that a considerable part of the actuating forceobtainable from bi-metallic strips is ordinarily wasted. Such stripscomprise the controlling element in of the ribbon.

temperature control devices and are usually made of two metalsfixed'together, having different coefficients of expansion, andsometimes being formed in the shape of aspiral. The purpose of such anarrangement is, of course, to use'the Spiral strip to turn or rotate atemperature `control device in response to temperature changes in thebi-metallic strip.

. I find, however, that where the spiral stripI 30 is in the form of aribbon of considerable width, temperature changes will not onlyv tend torotate one end of the ribbon with respect to the other, but will alsotend to curl each and every' cross-sectional portion Thiscross-Sectional curling of the strip will strengthen the strip iagainstrotational effects. and thereby greatly diminish the effectiveness ofthe strip in controlling the temperature device.

A11 object of my invention is, therefore,

to provide an improved design of bi-metallic str-1p having means forminimizing the bending stresses in a crosswise direction, therebyincreasing the rotational ability produced 4by expansion and contractionlengthwise, and permitting this lengthwise expansion and contraction too erate unhampered Aby any tendency of the bi-metallic strip tostrengthen itself against such action by curling.

' In the drawings wherein I have illustrated" Van embodiment of the myinvention:

' Figure 1 1s a top plan view of abi-metallic strip embodying myinvention:

preferred form of Fig.l 2 is a cross-sectional view of the same;

Fig. 3 illustrates in cross section the manner in which a bi-metallicstrip will curl when not embodying my invention;

Fig. 4 illustrates in cross section the manner inv which a bi-metallicstrip Vwill cur-l when embodying my invention and Fig. 5 is a Sideelevational view of this strip formed in a spiral.

In the drawings the bi-metallic Strip 5 of the thermostatic coil isillustrated as comprising an inner metal 6 and an outer metal 7, theline of junction being-'shown at `8'. The two metals are Vsoldered orbrazed together, so that the full effect of the Ldifferent expansions isobtained, there being no' possible slipping of one metal on the other. Iemploy two metals, Such as differ atleast in expansibility landmay bereadily united by soldering or brazing. I prefer invar Steel, or thelike, for the outer metal and bnass, or its alloys as the innermetal,but other combinations may be made with success; l

An important feature ofthe present invention is the form given to theouter metal 7 of the ribbon or strip forming the spiral.

tically unnoticeable and unable to strengthen the bi-metallic stripagainst rotational effects. e

Wheny formed spirally, the bi-metalllc Strip 5 is-usually quite wide. Ifso desired, more than one lon ltudinal oove 9Y mayibe provided, but thisis entirely dependent upon the width of the strip. .Moreoven the coil ismade more sensitive with thls groove which admirably Serves as means forincreasing the eiic'iency during expanslon and centraction. vWhenimparting the actuating force, a liner degree of sensltlveness or promptresponse is notlceable, beoaruse the lengthwise expansion andcontraction (which are the rotational effects produced) lare unhamperedand freeto act, without transverse bending stresses interfering.

It is believed that the principle underlying this invention, itsfunctional law,A and the merits and advantages which it possesses willbe entirely clear to those skilled in the art without further detaileddescription of other equivalent specific forms in which the inventionmay obviously be embodied.

Hence, without limiting the invention to.

the particular embodiment thereof herein selected forpurposesl ofillustration and. description l I claim: 1. A bi-vmetallic elementhaving at least i one of its metals devided into a pliiialit1 of strips.4- E I 2. A thermostatic coil comprising metals of differentcoefficients of expansion and having at least one of said metals dividedbe` tween its edges to minimize the bending stresses in a crosswisedirection. Y 3. Means for increasing the rotational 4:. Means forincreasing the rotational..

effects of a spirally forme-d bi-metallic element comprising theprovision of at least two strips serving as one of the metals, saidstrips being disposed along the edges of the other metal so as tolocalize the -crosssectioiral bending stresses adjacent theoutei' edgeportions thereof.

5. A bi-metallic element` of substantial width havingits ou'ter metallseparated so as to reduce cross-sectional curling of said element. l

6. A bi-metallicA element of. substantial width having at least one ofits metals of such formation as to reduce cross-sectional(v curling ofsaid element.` l

In witness whereof, I have hereunto1subscribed my name.y

Louis A. M. PHELAN.

